1. Field of the Invention
The present invention relates to a dry battery driven liquid pump and more particularly to an improved liquid pump adapted to be driven with a plurality of dry cells contained as a driving power source in a dry battery casing so as to effect forcible pumping of liquid such as kerosene or the like into a tank for an oil heater or the like in such a manner that pumping stops automatically by means of a liquid surface detector without any danger of causing an overflow from the tank when liquid is filled to a predetermined level therein.
2. Description of the Prior Art
Japanese U.M. Publication Nos. 53-105101 and 47-16015 disclose a known dry battery driven liquid pump with an automatic pumping operation stop device incorporated therein is generally equipped with a float switch which detects a liquid surface level in the tank. To fit the float switch in a delivery tube of the liquid pump it is inevitably necessary that the delivery tube has an inner diameter larger than 30 mm. This causes the liquid pump to be rather large. Another drawback inherent in the conventional liquid pump of the above type is that it fails to stop pumping due to malfunction of the float switch caused when the liquid pump is operated while it is held at a certain inclination or when foreign material is included in liquid to be pumped. As a result, pumped liquid overflows from the tank.